Welding apparatus

ABSTRACT

Welding apparatus comprising a mounting structure, means for mounting the mounting structure upon two opposed walls so that the mounting structure spans the space between the walls, guide means carried by the mounting structure, the guide means extending generally parallel to the mounting structure and almost spanning the space between the walls, means for adjustably automatically the guide means and fastening the same transversely desired angular positions between the two opposed walls and weld depositing means movable along the guide means to deposit a bead of weld metal on a surface between the two opposed walls. The means for mounting the mounting structure upon the two opposed walls may include brackets appliable, as, for example, by welding, to the walls. The brackets may be designed to provide for horizontal adjustment of the mounting structure parallel to the two opposed walls. The mounting structure is preferably turnable between the two opposed walls to adjustably position the guide means in desired angular positions and the mounting structure may have means operable to engage at least one of the two opposed walls to fasten the mounting structure in position with respect thereto. The mounting structure may be trunnioned in the brackets to turn relatively thereto to adjustably position the guide means in desired angular position, and friction clamping means may be provided acting between the mounting structure and at least one of the two opposed walls to fasten the mounting structure in position with respect thereto. The friction clamping means may comprise opposed friction clamps carried by the mounting structure adapted to engage the respective opposed walls. Means are preferably provided for adjustably positioning the weld depositing means transversely of the guide means so that beads of weld metal may be deposited at different controlled locations upon successive passes of the weld depositing means along the guide means for each position in which the guide means are fastened. Means may be provided automatically adjusting the position of the weld-depositing means transversely of the guide means.

United States Patent Hubert J. Anderson Primary Examiner-4. V. Truhe Assistant Examiner-George A. Montanye Attorney-Edward Hoopes, I11

ABSTRACT: Welding apparatus comprising a mounting structure, means for mounting the mounting structure upon two opposed walls so that the mounting structure spans the space between the walls, guide means carried by the mounting structure, the guide means extending generally parallel to the mounting structure and almost spanning the space between the walls, means for adjustably automatically the guide means and fastening the same transversely desired angular positions between the two opposed walls and weld depositing means movable along the guide means to deposit a bead of weld metal on a surface between the two opposed walls. The means for mounting the mounting structure upon the two opposed walls may include brackets appliable, as, for example, by welding, to the walls. The brackets may be designed to provide for horizontal adjustment of the mounting structure parallel to the two opposed walls. The mounting structure is preferably tumable between the two opposed walls to adjustably position the guide means in desired angular positions and the mounting structure may have means operable to engage at least one of thetwo opposed walls to fasten the mounting structure in position with respect thereto. The mounting structure may be trunnioned in the brackets to turn relatively thereto to adjustably position the guide means in desired angular position, and friction clamping means may be provided acting between the mounting structure and at least one of the two opposed walls to fasten the mounting structure in position with respect thereto. The friction clamping means may comprise opposed friction clamps carried by the mounting structure adapted to engage the respective opposed walls.

Means are preferably provided for adjustably positioning the weld depositing means transversely of the guide means so that beads of weld metal may be deposited at different con trolled locations upon successive passes of the weld depositing means along the guide means for each position in which the guide means are fastened. Means may be provided automatically adjusting the position of the weld-depositing means transversely of the guide means.

PATENTED JUL20I97I SHEET 1 BF 5 FIG. 2.

HUBERT J. ANDERSON ENTOR um WM HIS ATTORNEY PATENTEU JUL20 I97! SHEET 3 OF 5 WELDING APPARATUS This invention relates to welding apparatus and especially to welding apparatus which is primarily adapted and intended forresurfacing impact crusher impellers although the apparatus is adapted for other uses. For purposes of explanation and illustration the invention will be described as embodied in welding apparatus-for resurfacing impact crusher impellers. I

An impact crusher comprises a body or casing in which an impeller in the formof a'drum is mounted for rotation with means for rotating the drum at high speed. The impeller drum is of generally cylindrical shape mounted in'the casing for rotation about its axis and normally oriented with its axis horizontal. On the surface of the drum is-or are one or more heavy manganese steel bars. The number of bars on a drum may vary from one to several; Also the number of drums in a crusher may vary, but for purposes of illustration l have selected a crusher containing but a single impeller drum.

The drum when mounted in the casing of the impact crusher substantially spans the space between the sidewalls of the crusher. A typical size range of drum is 30 to 50 inches in diameter and 24 to 6.0 inches in axial dimension. The heavy manganese steelbars may be secured to the drum by clamps or bolts or by welding. The interior walls of the crusher casing are'lined with heavy manganese steel plates to take the impact of the material, such as rock, being crushed. The crushing procedure is to rotate the drum at high speed and feed the material to be crushed into the crusher so that the impact bars strike the material and cause fracture and breaking up thereof.

The crusher bar or bars on the impeller drum of an impact crusher become worn down in use and have to be either replaced or resurfaced by building up with weld metal. It is undesirable to have to dismantle a crusher and remove the drum to replace or resurface the bars, but because of the confined space in the crusher it is difficult to apply weld metal to the bars when the drum is in place in the crusher. Proposals have heretofore been made to apply weld metal to the crusher bars on a drum in place in an impact crusher but no fully satisfactory equipment for that purpose has been devised prior to my invention.

I provide welding apparatus which I have designed specifically for use in an impact crusher for applying weld metal to the'crusher bars without removing the drum from the crusher although my apparatus has other uses, particularly in situations in which it must be mounted between confining sidewalls. My welding apparatus may comprise a mounting structure, means for mounting the mounting structure upon two opposed walls so that the mounting structure spans the space between the walls, guide means carried by the mounting structure, the guide means extending generally parallel to the mounting structure and almost spanning the space-between the walls, means for adjustably positioning the guide means and fastening the same in desired angular positions between the two opposed walls and weld depositing means movable along the guide means to deposit a bead of weld metal on a surface between the two opposed walls. The means for mounting the mounting structure upon the two opposed walls may include brackets appliable, as, for example, by welding, to the walls. The brackets may be designed to provide for horizontal adjustment of the mounting structure parallel to the two opposed walls. The mounting structure is preferably turnable between the two opposed walls to adjustably position-the guide means in desired angular positions and the' mounting structure may have means operable to engage at least one of the two opposed walls to fasten the mounting structure in position with respect thereto. The mounting structure may be trunnioned in the brackets to turn relatively thereto to adjustably position the guide means in desired angular positions, and friction clamping means may be provided acting between the mounting structure and at least one of the two opposed walls to fasten the mounting structure in position with respect thereto. The friction clamping means may comprise opposed means along the guide means foreach position in which the guide means are fastened. Means may be provided automatically adjusting the position of the weld depositing means transversely of the guide means.

More specifically I provide welding apparatus for resurfacing impact crusher impellers comprising drilled brackets adapted to be applied in opposed relationship to the sides of an impact crusher casing, a mounting structure spanning the casing generally parallel to the axis of the impeller and having trunnions joumaled in the drilled brackets so that the mount ing structure may be tumed'to selected angular positions, friction clamping means for fastening the mounting structure in said positions, guide means carried by the mounting structure extending generally parallel to the mounting structure, means movable along the guide means to deposit weld metal on the impeller and means for adjustably positioning, preferably au tomatically, the last-mentioned means transversely of the guide means for each pass thereof along the guide means.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawings 1 have shown a present preferred embodiment of the invention in which FIG. 1 is a fragmentary isometric view showing the upper portion of the casing'of an impact crusher with an impeller drum mounted therein for rotation about its horizontal axis and showing the crusher bars on the drum, this figure also showing brackets welded to the opposed sidewalls of the easing interiorly thereof for supporting the welding apparatus;

FIG. 1A is a reduced scale fragmentary view similar to FIG. 1 but showing brackets of modified form designed to provide for horizontal adjustment of the mounting structure parallel to the opposed sidewalls of the casing;

FIG. 2 is a more or less diagrammatic vertical cross-sectional view through an impact crusher taken perpendicular to the axis of the impeller drum and showing the welding ap paratus mounted on the brackets which are welded to the opposed sidewalls of the casing (in this figure portions of the welding apparatus are omitted for clarity of showing of the parts which do appear and in view of the relatively small scale of the figure); I

FIG. 3 is an elevational view, partly in vertical cross section, to enlarged scale of the welding apparatus shown diagrammatically at the upper portion of HO. 2;

FIG. 4 is a fragmentary horizontal cross-sectional view showing part of the casing and also showing part of the welding apparatus on the line lV-lV of FIG. 3',

FIG. 5 is a fragmentary view, partly'in elevation and partly in vertical cross section, of a portion of the apparatus; and

FIG. 6 is a front view of the control panel for the apparatus.

Referring now more particularly to the drawings, there is shown somewhat diagrammatically an impact crusher comprising a casing 2 having mounted therein for rotation about its horizontal axis an impeller drum 3 having three manganese steel bars 4 welded to its periphery at equally spaced locations. The axial dimension of the drum 3 is but slightly less than the distance between the sidewalls 5 of the casing 2 so that the drum substantially spans the space between the sidewalls of the casing. Means not shown are provided for rotating the drum 3 at high speed as well known to those skilled in the art. The impact crusher illustrated herein may be deemed to be of conventional construction so description of its detail is unnecessary. The interior walls of the casing 2 are covered with manganese steel plates. with the drum rotating at high speed the material to be crushed is fed into the casing where it is impacted by the bars 4 and impelled against the interio'r walls of the casing and thereby fractured and broken up.

As above stated the bars 4 become worn down in use and have to be eitherreplaced or resurfaced by building up with weld metal.

It is of course possible to dismantle the crusher and remove the drum for resurfacing of the bars but this is undesirable since the drum is ponderous and difficult to remove and replace. On the other hand difficulty has been experienced in mounting welding apparatus in the casing to resurface or build up the bars by the application of weld metal thereto while the drum is in place in the casing. l have conceived the provision of two brackets which may be supplied as loose parts with the welding apparatus, such brackets to be applied as by welding to the interior of the opposed sidewalls of the casing to support the welding apparatus. I have shown in FIG. 1 brackets designated respectively by reference numerals 6 and 7. These brackets may be made of steel and drilled, the bracket 6 having a bore 8 therethrough while the bracket 7 has a similar bore with a slot 9 extending from the bore to the upper edge of the bracket. I may here mention that this means of providing for the mounting of welding apparatus between two opposed walls while especially applicable to impact crushers is not limited thereto and may be employed in any situation where welding apparatus is to be mounted between opposed confining walls. v

FIG. 1A shows brackets 6a which may be employed instead of the brackets 6 and 7 of FIG. 1. Each of the brackets 6a is provided with a slot of inverted T shape having a generally horizontal elongated slot 8a with which a vertical slot 9a communicates. Asshown the vertical slot 9a of each of the brackets 6a may flare to increased width upwardly to facilitate application of the mounting structure. When the mounting structure is applied the pins 11 thereof may simply] pass downwardly through the slots 9a into the slots 8a. Thus with the form of bracket of FIG. 1A it is not necessary to mount the pins 11 for retraction and projection into the brackets. Also the form of bracket of FIG. 1A provides for horizontal adjustment of the mounting structure parallel to the walls 5 which is a considerable advantage in disposing the welding apparatus in optimum position relative to the work.

The welding apparatus comprises a mounting structure designated generally by reference numeral 10 having at opposite ends thereof trunnions in the form of coaxial pins 11 adapted to be projected to enter the brackets. Any suitable means may be provided for mounting the trunnion pins in the mounting structure 10 for projection into the brackets and maintaining them in projected positiomThereby the mounting structure 10 is mounted in the casing 2 and is turnable through a limited angle about the axis of the trunnion pins 11. The mounting structurel substantially spans the space between the sidewalls of the casing 2 and has at each end an overcenter friction clamp 12 having a contact or nose portion 13 of rubber or similar antifriction material adapted to be pressed firmly against the inner surface of the corresponding sidewall 5 whereby to maintain the mounting structure in desired angular positions about the axis of the trunnion pins 11 and also, when the brackets of FIG. IA are employed, in desired positions along the horizontal slots'8a. when a bar 4 is to be built up by the application thereto of weld metal the drum 3 is turned to position the bar at the most convenient location for welding and the drum is held in that position. Then the mounting structure 10 is disposed in optimum position for welding and clamped in that position by the clamps l2.

The mounting structure 10 has guide means comprising spaced-apart parallel bars 14 upon which the welding carriage is mounted and guided for movement across the casing 2 or along the bar 4 to which weld metal is to be applied. The weld-- ing carriage is designated generally by reference numeral 15 and comprises a bronze block 16 mounted between the bars 14 for guided movement therealong. Connected with the bronze block l6'is a sprocket chain 17 extending about sprockets l8 and 19 and about a sprocket 20 driven by an electric motor 21 through suitable reduction gearing. The motor 21 is a reversible motor and when it is energized it moves the welding carriage 15 in one direction or the other 7 above the bar 4 to which weld metal is to be applied. The

welding nozzle clamp is mounted on and carried b y ah0rizontal threaded rod or screw 25. Mounted on the carriage is an electric motor 26 driving through suitable reduction gearing a bevel gear 27 meshing with a bevel gear 28 which is internally threaded and acts as a nut on the threaded rod 25. Axial movement of the bevel gear 28 is prevented by thrust bearings 29. Operation of the motor 26 causes rotation in place of the bevel gear 28 which, because'it is in threaded engagement with the threaded rod 25, causes the threaded rod 25 to move axially, carrying with it the nozzle clamp 23 and the welding nozzle 24. The nozzle clamp also carries a guide rod 30 extending through a bearing guide 31 in the carriage which prevents turning of the nozzle clamp and'also stabilizes it in the vertical position. It is protected from weld spattcr by a protective guard 32. The exposed parts of the threaded rod 25 and the guide rod 30 are protected by flexible boots 33 of ac cordion pleated canvas which can expand and contract without binding the mechanism.

Limit switches 34 are provided to limit the movement of the nozzle clamp. The rod 25 carries a cam 35 which operates one or the other of the limit switches 34 depending upon the direction of movement. Operation of either of those limit switches stops operation of the electric motor 26.

A wire feeder which may be of conventional construction is provided for feeding'welding wire through the welding nozzle 24, the welding wire being fed from any suitable source of such wire as well known to those skilled in the art.

The control circuitry for the apparatus may assume an infinite variety of forms and once the functions to be performed are specified may be designed by any controls designer. I have shown in FIG. 6 the control panel for the apparatus and I shall mention the control functions to be performed and identify the elements on the control panel for effecting the control operations. y

Referring now to FIG. 6; the control of the speed of movement of the welding carriage I5 is effected by a knob 36 of a variable voltage transformer which controls the speed of the motor 21 by varying the armature voltage. The switch 37 is the overall control switch for turning on and shutting off the input power to the control system. The knob 38 controls step distance of the nozzle clamp 23, i.e;, it controls the time of operation of the motor 26. The welding carriage selector switch 39 has pilot lights 40 to the left and right of the switch indicating the direction of travel of the welding carriage. The off-on switch 41 simply provides power to the carriage travel circuit. Switch 39 permits reversing the welding carriage in any position along its path of travel independentof the limit switches hereinabove described. v

Referring further to FIG. 6, the switch 42 controls the in and out or step movement of the nozzle clamp 23. Switch 43 has an off" position, a run position and an automatic position and when it is in the automatic position the nozzle clamp 23 will move in or out, depending upon the position of the switch 42, a predetermined distance as a function of the step distance adjustment effected by the knob 38; it will step each time'the carriage is reversed. When the switch 43 is in the run position the nozzle clamp 23 will move in or out continuously until one or the other of the limit switches 34 is actuated by the cam 35 or the operator turns the switch 43 to the "off" position.

Elements 44 are fuse holders for the circuits for the motors 21 and 26 respectively.

When a bar 4 is to bc resurfaced the impeller drum 3 is turned to the optimum position for application of weld metal to the bar and is fastened in that position so that it will not turn during the welding. FIG. 2 shows the drum positioned with the bar to be welded disposed directly upwardly. While this normally would be, deemed to be the optimum position for application of weld metal to the bar, in some instances operators may prefer to have the bar disposed a few degrees one way or the other from the position shown in FIG. 2. The welding nozzle 24 is disposed in the position above the bar which will enable weld metal to be applied along the bar at the desired location. Operation of the welding carriage and wire feeder is initiated and the carriage moves along the bar as weld metal is applied to the bar. The limit switches for control of the welding carriage are set so that as the welding nozzle 24 reaches an end of the bar 4 its direction is reversed. At the same time the welding nozzle is stepped inwardly or outwardly either automatically or manually as desired so that the succeeding bead of weld metal is disposed at a desired location alongside the first bead. As above indicated the controls are such that the welding nozzle may step in or out continuously during movement of the welding carriage along the bar, but ordinarily this would not be done as the optimum procedure in most cases is to apply parallel weld beads to the bar.

Thus I have provided apparatus for applying weld metal to an element positioned between two opposed confining walls including novel and extremely simple and inexpensive means for mounting the welding apparatus between and upon such walls. My invention makes feasible and economical the resurfacing of the bars of an impact crusher without removing the impeller drum from the casing and without the relativelycomplex and costly mechanism heretofore proposed for such purpose.

While I have shown and described a present preferred embodiment of the invention it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

lclaim:

1. Apparatus comprising two opposed spaced-apart generally parallel generally vertical walls having opposed faces and top edge portions, said walls defining a space therebetwcen in which a workpiece is disposed between said walls and below the top edge portions thereof, a mounting structure, means on the opposed faces of said walls at substantially the same elevation and below the top edge portions of said walls for mounting the mounting structure between said walls so that the mounting structure spans the space therebetwcen, guide means carried by the mounting structure, the guide means extending generally parallel to the mounting structure and disposed between said walls and rotatable about an axis generally perpendicular to said walls, means for adjustably positioning the guide means about said axis and weld depositing means attached to the guide means for travel therealong for depositing weld metal on the workpiece.

2. Apparatus as claimed in claim 1 in which the mounting structure has means pivotally mounting it on the two opposed walls whereby the mounting structure is turnable between the two opposed walls to adjustably position the guide means in desired angular positions and the mounting structure has means operable to engage at least one of the two opposed walls to fasten the mounting structure in position withrespect thereto.

3. Apparatus as claimed in claim 2 in which means are provided for adjustably positioning the weld depositing means transversely of the guide means so that beads of weld metal may be deposited at difi'erent controlled locations upon successive passes of the weld-depositing means along the guide means for each position in which the guide means are fastened.

4. Apparatus as claimed in claim 3 including means automatically adjusting the position of the weld-depositing means transversely of the guide means for each pass of the weld depositing means along the guide means.

. Apparatus as claimed tn claim 1 in which means are provided for adjustably positioning the weld-depositing means transversely of the guide means so that beads of weld metal may be deposited at different controlled locations upon successive passes of the weld-depositing means along the guide means for each position in which the guide means are fastened.

6. Apparatus as claimed in claim 5 including means automatically adjusting the position of the weld-depositing means transversely of the guide means for each pass of the weld depositing means along the guide means.

7. Apparatus as claimed in claim 1 in which the means for mounting the mounting structure between the walls include brackets applied to the walls.

8. Apparatus as claimed in claim 7 in which the brackets have generally elongated slots in which the mounting structure is mounted providing for horizontal adjustment of the mounting structure parallel to the two opposed walls.

9. Apparatus as claimed in claim 7 in which the brackets are welded to the walls.

10. Apparatus as claimed in claim 7 in which trunnion means are provided on which the mounting structure is trunnioned in the brackets to turn relatively thereto to adjustably position the guide means in desired angular positions and friction clamping means are provided acting between the mounting structure and at least one of the two opposed walls to fasten the mounting structure in position with respect thereto.

11. Apparatus as claimed in claim 10 in which the friction clamping means are opposed friction clamps carried by the mounting structure constructed and arranged to engage the respective opposed walls to fasten the mounting structure in position with respect thereto.

12. Welding apparatus comprising two opposed spacedapart generally parallel, generally vertical walls having opposed faces and top edge portions, said walls defining a space therebetwcen in which an impact crusher impeller is disposed between said walls and below the top edge portions thereof, and brackets attached to the opposed faces at substantially the same elevation and below the top edge portions, a mounting structure spanning the space between the walls and generally parallel to the axis of the impeller and having trunnions journaled in the brackets so that the mounting structure may be turned to selected angular positions, friction clamping means for fastening the mounting structure in said positions, guide means carried by the mounting structure extending generally parallel to the mounting structure, means movable along the guide means to deposit weld metal on the impeller and means for adjustably positioning the last-mentioned means transversely of the guide means.

13. Welding apparatus comprising two opposed spacedapart generally parallel, generally vertical walls having opposed faces and top edge portions, said walls defining a space therebetwcen in which an impact crusher impeller is disposed between said walls and below the top edge portions thereof, and brackets attached to the opposed faces at substantially the same elevation and below the top edge portions, a mounting structure spanning the space between the walls and generally parallel to the axis of the impeller and having trunnions journaled in the brackets so that the mounting structure may be turned to selected angular positions, friction clamping means for fastening the mounting structure in said positions, guide means carried by the mounting structure extending generally parallel to the mounting structure, means movable along the guide means to deposit weld metal on the impeller and means automatically adjusting the position of the last-mentioned means transversely of the guide means for each pass thereof along the guide means. 

1. Apparatus comprising two opposed spaced-apart generally parallel generally vertical walls having opposed faces and top edge portions, said walls defining a space therebetween in which a workpiece is disposed between said walls and below the top edge portions thereof, a mounting structure, means on the opposed faces of said walls at substantially the same elevation and below the top edge portions of said walls for mounting the mounting structure between said walls so that the mounting structure spans the space therebetween, guide means carried by the mounting structure, the guide means extending generally parallel to the mounting structure and disposed between said walls and rotatable about an axis generally perpendicular to said walls, means for adjustably positioning the guide means about said axis and weld depositing means attached to the guide means for travel therealong for depositing weld metal on the workpiece.
 2. Apparatus as claimed in claim 1 in which the mounting structure has means pivotally mounting it on the two opposed walls whereby the mounting structure is turnable between the two opposed walls to adjustably position the guide means in desired angular positions and the mounting structure has means operable to engage at least one of the two opposed walls to fasten the mounting structure in position with respect thereto.
 3. Apparatus as claimed in claim 2 in which means are provided for adjustably positioning the weld depositing means transversely of the guide means so that beads of weld metal may be deposited at different controlled locations upon successive passes of the weld-depositing means along the guide means for each position in which the guide means are fastened.
 4. Apparatus as claimed in claim 3 including means automatically adjusting the position of the weld-depositing means transversely of the guide means for each pass of the weld depositing means along the guide means.
 5. Apparatus as claimed in claim 1 in which means are provided for adjustably positioning the weld-depositing means transversely of the guide means so that beads of weld metal may be deposited at different controlled locations upon successive passes of the weld-depositing means along the guide means for each position in which the guide means are fastened.
 6. Apparatus as claimed in claim 5 including means automatically adjusting the position of the weld-depositing means transversely of the guide means for each pass of the weld depositing means along the guide means.
 7. Apparatus as claimed in claim 1 in which the means for mounting the mounting structure between the walls include brackets applied to the walls.
 8. Apparatus as claimed in claim 7 in which the brackets have generally elongated slots in which the mounting structure is mounted providing for horizontal adjustment of the mounting structure parallel to the two opposed walls.
 9. Apparatus as claimed in claim 7 in which the brackets are welded to the walls.
 10. Apparatus as claimed in claim 7 in which trunnion means are provided on which the mounting structure is trunnioned in the brackets to turn relatively thereto to adjustably position the guide means in desired angular positions and friction clamping means are provided acting between the mounting structure and at least one of the two opposed walls to fasten the mounting structure in position with respect thereto.
 11. Apparatus as claimed in claim 10 in which the friction clamping means are opposed friction clamps carried by the mounting structure constructed and arranged to engage the respective opposed walls to fasten the mounting structure in position with respect thereto.
 12. Welding apparatus comprising two opposed spaced-apart generally parallel, generally vertical walls having opposed faces and top edge portions, said walls defining a space therebetween in which an impact crusher impeller is disposed between said walls and below the top edge portions thereof, and brackets attached to the opposed faces at substantially the same elevation and below the top edge portions, a mounting structure spanning the space between the walls and generally parallel to the axis of the impeller and having trunnions journaled in the brackets so that the mounting structure may be turned to selected angular positions, friction clamping means for fastening the mounting structure in said positions, guide means carried by the mounting structure extending generally parallel to the mounting structure, means movable along the guide means to deposit weld metal on the impeller and means for adjustably positioning the last-mentioned means transversely of the guide means.
 13. Welding apparatus comprising two opposed spaced-apart generally parallel, generally vertical walls having opposed faces and top edge portions, said walls defining a space therebetween in which an impact crusher impeller is disposed between said walls and below the top edge portions thereof, and brackets attached to the opposed faces at substantially the same elevation and below the top edge portions, a mounting structure spanning the space between the walls and generally parallel to the axis of the impeller and having trunnions journaled in the brackets so that the mounting structure may be turned to selected angular positions, friction clamping means for fastening the mounting structure in said positions, guide means carried by the mounting structure extending generally parallel to the mounting structure, means movable along the guide means to deposit weld metal on the impeller and means automatically adjusting the position of the last-mentioned means transversely of the guide means for each pass thereof along the guide means. 